The invention relates generally to measuring devices, and more particularly a highly accurate device for mechanically locating a point which is at a desired fraction of the distance between two other points. It has many applications, such as in the construction industry, the drafting art, and around the home. Only two of several possible embodiments are needed to provide for a useful range of desired fractions.
Heretofore, when attempting to accurately measure half or one-third of the distance between two points it has been necessary first to measure the distance between the points, second to calculate the length of the desired fraction, and third to measure and mark that distance. Sometimes a caliper or micrometer has been used in conjunction with such measurements and calculators. In addition to being time consuming, a certain degree of error usually is inherent in such manual operations.
Another method of measuring desired fractions has been to traverse the distance with, for example, a rope, then fold the rope into halves or thirds, lay it along the original line and mark the desired point where the end of the fold falls. The inherent inaccuracy and time consumption of such a process is obvious.
The prior art does not provide an easily used, highly accurate device for locating the midpoint or one-third point of a desired distance. Devices such as rulers, calipers, micrometers, and measuring lines require a manual interaction, some calculation and probable inaccuracy. Remotely related solutions are found in the drapery art and in the hyperbolic position locator art.
Certain devices, as illustrated by U.S. Patents to Goudsmit, U.S. Pat. No. 2,562,664, and Johnson et al., U.S. Pat. No. 2,591,074, employ strings and pulleys to determine location as a function of the time it takes a radio signal to travel from a transmitting vessel to several receiving stations. The indicators are attached to moveable arms in a common plane, representing the receiving station, and are designed to vary distance in a hyperbolic function so that the intersection of the plotted lines indicates the position of the transmitter.
A more closely related technology is shown in Yaworsky and Morantz (U.S. Pat. Nos. 2,998,659 and 3,541,692) which teach the design of pleater gauges. These are used to determine where to put the pleats in a drapery composed of a number of pieces of material to be sewn together. The devices entail a series of indicator elements attached to each other and to a lead element by a series of lines. In Yaworsky different sized pulleys are used to provide for simultaneous differential expansion. By setting the complex mechanism of the gauge for the total width to be covered and for the number of pieces of materials being combined, the markers would be drawn out symetrically across the material showing where the pleats are to be located. Such devices are far more complex and serve a different function than the device of the present invention. Moreover, none of them teaches the novel arrangement of indicators and cord paths of the invention.
None of the prior art teaches a simple, compact and easy-to-use device for mechanically determining halves, thirds, and related fractions with a high degree of accuracy.
It is therefore an object of the invention to provide a device for readily indicating the location of a desired fraction of a total distance with a high degree of accuracy.
Another aspect of the invention provides a point locator device having a leading and a trailing indicator connected by a single line which passes over a number of pulleys so that the trailing indicator will be accurately drawn a desired fraction of the distance which the leading indicator is drawn, in the same direction.
A further aspect of the invention is the provision of a device which may be used with a high degree of accuracy and which retains that accuracy despite continued use, being resistant to forces applied to the indicators which would tend to alter this mechanical relationship between the indicators.